METEOROLOGICAL REPORT. 



By THOMAS M. LOGAN, M. D., Meteorologist to the State Board of Agriculture. 



It has been claimed that the extension of civilization, the pursuit of 

 agriculture, the drainage and reclamation of vast tracts of marshes, and 

 particularly the felling of forests, have made great changes in the climate 

 of the United States, especially in respect to temperature and rainfall. 

 But whatever of truth there may be in the theories of man's agency 

 in modifying climate, we cannot go beyond the results of the records, 

 which have been made through a long series of years. Unsatisfactory 

 as these records may be, they nevertheless constitute the only reliable 

 data that we have for determining whether either of the climatic con- 

 ditions just referred to are increasing or diminishing — stationary or 

 periodic. 



From an examination of the results of all the observations which 

 have been collected by Professor Henry and published in the reports of 

 the Smithsonian Institution, we find that there has been no material 

 change in the average rainfall, when long periods of time are com- 

 pared, however the annual amount may vary. The irregularities in the 

 successive yearly precipitation, though found to be vei'y great in the 

 different groups of the stations where the observations were made, and 

 into which they were classed for the purpose of being systematically 

 studied, nevertheless do not obliterate the aj>pearance of conformity to 

 general laws. The only decided indications of any material change are 

 found in «groups one and two, comprising New England and the Middle 

 States, where the rainfall seems to have steadily increased since the 

 year eighteen hundred and eighteen, in the very district which has been 

 most stripped of its clothing of forest. Thus the power of augmenting 

 the fall of rain which has been largely attributed to trees, vaguely by 

 some, who confound such an attribute with their power of attracting 

 mists, and boldly by others, who assert that rain now falls where trees 

 have been planted in tracts formerly rainless, cannot longer be logically 

 entertained. We learn positively from the mean results, as tabulated, 

 that the rainfall during one hundred and thirty-seven years has under- 

 gone no change on this continent. The humidity of the great aerial 

 currents is quite independent of local causes. The winds, charged with 

 moisture collected in other regions, discharge their rain with indiffer- 



